The safety belts used in motor vehicles, frequently used in conjunction with belt pre-tensioners which are controlled by the operating state of the vehicle, are generally 46 mm to 48 mm wide. They are intended to protect the occupant of the vehicle during an accident from uncontrolled swirling movements within the vehicle, which are associated with considerable risks of injury, but without excessively limiting the freedom of movement of the occupant under normal operating conditions. These safety belts have proved to be extremely effective in practice and since their general introduction into road transport they have made a significant contribution to reducing serious injuries as a result of an accident.
In contrast, the width dimensions actually used of such a belt are not regarded as being optimal, since during an accident, in accordance with the value of the forces which are to be transmitted via the belt, localised excessively high loadings, which are concentrated in accordance with the width dimensions, can occur on the body with the associated risks of injury, which can be considerable in particular when the body of the vehicle occupant is in an unfavourable position. These width dimensions actually used were also introduced at that time under the consideration of representing an increase in travel safety, whilst on the other hand impairing the travel comfort as little as possible.
In order to reduce the risks of injury whilst maintaining the travel comfort a safety belt system is known from the document DE 43 26 499 A1, whose belt comprises a tube-like structure which is connected to a gas-generating device. The gas-generating device which can be activated by a delaying sensor is adapted to generate a high pressure gas which influences the said structure and which is designed with the proviso that it practically does not extend in the lengthwise direction of the belt at all, but considerably extends in the transverse direction thereto, thus increasing the width of the belt in an emergency situation and hereby in association reducing the risk of injury of the vehicle occupant who is strapped in. The structure consists of two belt-band base fabric parts which comprise individually the width of a conventional safety belt and which are stitched together along their longitudinal edges, whose fabrics consisting of warp and weft threads are each characterised by the fact that the warp threads extend in the lengthwise direction and the weft threads extend in the transverse direction to the belt band. To demonstrate the different stretching properties mentioned in the introduction in the transverse and lengthwise direction of the belt, the warp threads consist of an extremely rigid material which practically does not stretch, whereas the weft threads in contrast consist of a rubber-like stretchable material, e.g. polyurethane. In order to achieve these stretching properties, a not inconsiderable expenditure is necessary which is expressed in a tube-like belt structure, a delaying sensor and a gas-generating device.